ATRN and early-onset autosomal dominant Alzheimer disease: In humans, ATRN is a candidate gene for sporadic amyotrophic lateral sclerosis (Morahan et al., 2009), ATRN plasma levels are altered in early-onset Alzheimer’s disease (AD) patients prior to symptoms (Muenchhoff et al., 2016), and its gene expression is reduced in Parkinson disease (PD) patients (Glaab and Schneider, 2015).